Sphygmomanometer

ABSTRACT

The invention relates to a cuff for a sphygmomanometer, which is able to judge the maximum blood pressure and minimum blood pressure at a high accuracy. The cuff 10 comprises a bendably deformable hard curved plate 10a, an outside cloth 10b which surrounds the outer periphery of said curved plate 10a, an inside cloth 10c sewed to the outside cloth 10b so that the same surrounds the inner periphery of said curved plate 10a, an air bag 10d secured inside the inside cloth 10c, and an engaging fastener 10e sewed to the outer periphery of the outside cloth 10b. The air bag 10d is composed of a transparent bag member 10g in which reinforcing fabric 10f is incorporated in a latticed state. Each optical range sensor 12 is composed of a photocoupler 12a fixed at the outside of the bag member 10g and a reflection plate 12b fixed at the inside of the bag member 10g so as to be opposite to the photocoupler 12a. The photocoupler 12a has a light emitting diode and a phototransistor, whereby light emitted by the light emitting diode is reflected by the reflection plate 12b and is made incident into the phototransistor, and the output of the phototransistor may change in accordance with the distance between the photocoupler 12a and the reflection plate 12b.

FIELD OF THE INVENTION

The present invention relates to a cuff for a sphygmomanometer, and inparticular relates to a cuff used for a closed type sphygmomanometer.

BACKGROUND OF THE INVENTION

A closed type electronic sphygmomanometer in which a cuff pressing theartery is wound on the upper arm of a patient is already known. For atonometry hemadynamometry method with this kind of sphygmomanometer,although there are an oscillometric process, a Korotoff's sound method,an impedance method, etc., the oscillometric process has been mainlyutilized in clinical applications. A sphygmomanometer in which atonometry hemadynamometry method utilizing such an oscillometric processis employed is disclosed by, for example, Japanese Patent PublicationNo. 28637 of 1994.

A sphygmomanometer disclosed in the above publication is basicallycomposed of a cuff having an air bag which is attached to the upper armof a patient and presses the artery by supplying air therein, a pressuresensor which is able to detect the superposed pressure of the droppressure and pulse pressure which change in said air bag of the cuff, ameasuring section which converts the values detected by said pressuresensor into digital signals, a digital data processing section which isable to obtain the maximum and minimum blood pressure values of apatient by using the cuff pressure detection signals outputted by saidmeasuring section as input data, and a display section which is able todisplay the maximum and minimum blood pressure values calculated by saiddigital data processing section.

With a sphygmomanometer constructed as described above, the maximum andminimum blood pressure values are judged by the digital data processingsection on the basis of fluctuations of the pulse pressure vibrationsand pulse wave amplitude while causing the pressure in the cuff to drop.However, there were the following shortcomings in this tonometryhemadynamometry method with such an oscillometric process.

That is, in the tonometry hemadynamometry method, as has beenrepresented by an in-artery catheter method, the method for measuringthe pressure applied to a blood vessel wall by determining one point ofthe artery of a patient is ideal. However, with the tonometryhemadynamometry method by the abovementioned oscillometric method, sincethe pressure fluctuations in an air bag of the cuff wound on the upperarm of a patient is detected and is used for measuring the bloodpressure, a pulse pressure appears even in the in-cuff pressure which ishigher than the maximum blood pressure or it is not clear to judge theminimum blood pressure.

With the tonometry hemadynamometry method with a conventionaloscillometric process, this results from detecting the mean pulsation ofthe artery spreading in the range of the cuff, and the pulsation is suchthat the artery wall displacement of the brachial artery resulting fromthe heartbeat is propagated as displacements of the skin surface andfurther the displacement of the skin surface causes the air capacity inthe air bag of the cuff to be changed, wherein this capacity change isdetected as a pressure change in the cuff. Resultantly, the displacementquantity of the artery wall is converted to the pressure fluctuation inthe cuff.

However, with such a method, since the displacement quantity of theartery wall is measured via air in the air bag of the cuff, it is notpossible to faithfully obtain the artery wall displacement with only thepulse pressure wave obtained from inside the cuff because of receivinginfluences outside the body such as compression characteristics of air,damping characteristics thereof, etc.

This also means that although constituents of Korotoff's sounds whichhave higher frequency constituents than the pulse pressure waves aresuperposed with the pulse waveforms in a cuff pressure dropping processfrom the maximum blood pressure to the minimum blood pressure in theblood pressure measurement and must appear, fluctuations of higherfrequency constituents such as Korotoff's sounds are not able to bepropagated since air is used as a propagation medium in the in-cuffpulse pressure waveform in the oscillometric process, and resultantly itseems that such constituents do not appear.

That is, in a tonometry hemadynamometry method with a conventionaloscillometric process, since a cuff is wound onto a long length of thebrachial artery which is the portion to be measured of a patient and thepulse pressure vibrations are detected as pressure fluctuations in thecuff pressure, the artery pressure of the artery wall at one point whichis ideal in the tonometry hemadynamometry method is not accuratelyreflected. Accordingly, a pulse pressure wave occurs in the cuffpressure which is more than the maximum blood pressure, and since thepulse pressure wave is propagated by using air as a medium, thefrequency propagation is adversely influenced by the compressioncharacteristics and damping characteristics of air, and a shortcoming iscaused, whereby Korotoff's sound propagation is hindered.

The present invention was developed in view of solving theseshortcomings, and it is therefore an object of the invention to providea cuff for a sphygmomanometer which is able to accurately measure theblood pressure by directly measuring a local artery wall displacement.

DISCLOSURE OF THE INVENTION

In order to solve the object, the invention provides a cuff for asphygmomanometer, which is attached to an appointed part of a patientand presses the artery by supplying air therein, and is characterized inhaving a hard curved plate retained between the inside and outsidecloths mutually sewed together, an engaging fastener fixed at the outersurface of said outside cloth, an air bag fixed in the innercircumferential side of said inside cloth, and a photoelectric sensorsinstalled between said inside and outside parts of said air bag.

Said photoelectric sensor may be composed of a reflection plate securedat the inside part of said air bag, and a light receiving element and alight emitting element secured at the outside part of said air bag.

Furthermore, said photoelectric sensor has a pair of light receiving andlight emitting elements, wherein one of the abovementioned elements maybe provided at the inside part of said air bag, and the other may beprovided at the outside part of said air bag.

Said air bag may be composed of a transparent bag member and a latticedreinforcing fabric integrally incorporated in this bag member.

Since a cuff for a sphygmomanometer constructed above is provided with ahard curved plate retained between the inside and outside clothsmutually sewed together, an engaging fastener fixed at the outer surfaceof said outside cloth, an air bag fixed in the inner circumferentialside of said inside cloth, and a photoelectric sensor installed betweensaid inside and outside parts of said air bag, it is possible todirectly measure the displacement quantity of a local artery wall by anphotoelectric sensor and to obtain the maximum and minimum bloodpressure values on the basis of this displacement quantity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a developed view showing a preferred embodiment of a cuff fora sphygmomanometer according to the invention,

FIG. 2 is a cross-sectional view showing major parts of the cuff for asphygmomanometer according to the invention,

FIG. 3 is a block diagram showing a construction of a sphygmomanometerin which a cuff according to the invention is incorporated, and

FIG. 4 is a wave form diagram showing one example of pulsation wavesdetected by the cuff for a sphygmomanometer shown in FIG. 1.

PREFERRED EMBODIMENT OF THE INVENTION

A preferred embodiment of the invention will be hereinafter concretelydescribed with reference to the accompanying drawings.

FIG. 1 and FIG. 2 show a preferred embodiment of a cuff for asphygmomanometer according to the invention. FIG. 3 shows one example ofa sphygmomanometer in which a cuff according to the invention isincorporated. A sphygmomanometer shown in the same drawing has a cuff10, photoelectric sensor 12, and a digital data processing section 14.The cuff 10 is attached to an appointed part of a patient, concretely tothe upper arm 16, the detail of which is shown in FIG. 1 and FIG. 2.

The cuff 10 shown in the same drawings is composed of a bendablydeformable hard curved plate 10a made of a thin synthetic resin andformed to be arcuately curved, an outside cloth 10b which surrounds theouter periphery of said curved plate 10a, an inside cloth 10c sewed tothe outside cloth 10b so that the same surrounds the inner periphery ofsaid curved plate 10a, an air bag 10d secured inside the inside cloth10c, and an engaging fastener 10e sewed to the outer periphery of theoutside cloth 10b in order to stop the end parts of the inside cloth10c.

The air bag 10d is composed of an enclosed transparent synthetic resinsheet made bag member 10g in which reinforcing fibers 10f areincorporated. Reinforcing fibers 10f are integrally incorporated inorder to prevent elongation of the air bag 10g due to pulsations whenthe same is being compressed. When inflating the air member 10g bysupplying air into the same air bag 10g via a tube 18 described later,it is possible to inflate the bag member 10g in proportion to thesupplying quantity of air.

A tube 18 for supplying air is caused to communicate with and isconnected to the inside of the bag member 10g. A pressure sensor 20 anda solenoid control valve 22 are connected to the outer end of the tube18. And a pump 24 which is able to send out air is connected to thesolenoid control valve 22, and both the solenoid control valve 22 andpump 24 are controlled by the pump controlling section 26.

Detection signals of the pressure sensor 20 are inputted into a digitaldata processing section 14 via a band pass filter 28 and an A/Dconverter 30. Control signals are sent from the digital data processingsection 14 to the pump control section 26 on the basis of detectionsignals of the pressure sensor 20. The photoelectric sensor 12 iscomposed of a photocoupler 12a fixed at the outer surface of the outsideparty of the bag member 10g and a reflection plate 12b fixed at theouter surface of the inside part of the bag member 10g so that the sameis opposite said photocoupler 12a.

Said photocoupler 12a is such that a light emitting diode is integrallyassembled together with a phototransistor, and it is set so that thelight emitted from the light emitting diode is reflected by thereflection plate 12b and is made incident into the phototransistor. Theoutput size of the phototransistor may change according to the distancebetween the photocoupler 12a and the reflection plate 12b, wherebyoutput signals are sent out in response to the displacement of theartery.

The light emitting diode of the photocoupler 12a is controlled to beturned on and off by a light emission control section 32 connected tothe digital data processing section 14. The digital data processingsection 14 is connected to the phototransistor of the photocoupler 12avia a band pass filter 34 and an A/D converter, whereby the detectionsignals of the transistor are digitalized and inputted into theprocessing section 14.

Furthermore, in this preferred embodiment, although a photocoupler 12aand a reflection plate 12b are disposed outside a bag member 10g sincethe bag member 10g is formed with a transparent synthetic resin sheet,the photocoupler 12a and reflection plate 12b may be disposed insidethereof if the bag member 10g is formed with a non-transparent syntheticresin sheet plate 10g.

Still furthermore, in a cuff 10 for a sphygmomanometer according to theinvention, the photoelectric sensor 12 may employ not only a combinationof a photocoupler 12a and a reflection plate 12b but also a combinationof a light emitting diode and a photocoupler. In this case, thesemembers may be disposed opposite each other at the inside and outside ofthe bag member 10g.

The digital data processing section 14 is composed of a so-calledmicrocomputer which includes a CPU and a memory, and a display section38 which displays the maximum and minimum blood pressure values isconnected to this digital data processing section 14 via an interface.

When measuring the blood pressure, firstly, a cuff 10 is attached to theupper arm 16 of a patient. At this time, the cuff 10 is set so that thereflection plate 12 is positioned on the artery of the upper arm 16, andis fixed with the cloths 10b,10c engaged with the engaging fastener 10e.

Furthermore, in this case, in order to cause the reflection plate 12b tobe positioned on the artery of the upper arm 16 of a patient withoutfail, for example, as shown by hypothetical lines in FIG. 1, if aplurality of optical range sensors 12 are disposed along thecircumferential direction, it is possible to cause any one of thephotoelectric sensors 12 to be positioned on the artery. In a case wherea plurality of photoelectric sensors are employed, the one which outputsthe largest output signal may be selected by comparing the output valuesof the respective sensors 12 when using a plurality of sensors 12.

Upon the completion of attaching a cuff 10, the preparation of bloodpressure measurement is completed. Therefore, output signals are sentout from the digital data processing section 14 to the solenoid valvecontrol section 22 thereby to cause the solenoid valve control valve 22to be opened. And the solenoid control valve 22 is controlled on thebasis of the detection signals of the pressure sensor 20, whereby aconstant speed compression control by which the pressure inside the airbag 10d of the cuff 10 is increased at a constant speed is carried out.

At this time, since with a cuff 10 of the preferred embodiment,reinforcing fabric 10f are incorporated in the bag member 10g of the airbag 10g in a latticed state and a non-elastic curved plate 10a is causedto intervene at the outer circumference of the bag member 10d, theelongation and contraction of the bag member 10d are regulated, and theoutward expansion of the bag member 10d is regulated by the curved plate10a, whereby the photoelectric sensor 12 is prevented from beingdisplaced.

Accordingly, the air bag 10d compresses the artery by inwardlydisplacing only the inside thereof with the outside of the air member10g maintained as it is.

Detection signals sent from the photoelectric sensor 12 are taken intothe digital data processing section 14 one after another. Since theoutput signals of this photoelectric sensor 12 includes partscorresponding to the expansion of the air bag 10d being compressed at aconstant speed, the photoelectric volumetric pulse wave signals obtainedby eliminating the parts corresponding to the constant speed compressionare calculated in the digital data processing section 14, and themaximum blood pressure and maximum blood pressure are judged on thesesignals.

Those shown in FIG. 4 are one of the examples of photoelectricvolumetric pulse wave signals. One example of a method for judging themaximum blood pressure and minimum blood pressure on the basis of thesephotoelectric volumetric pulse wave signals will be described below. Forexample, herein it is assumed that the photoelectric volumetric pulsewave signals P1, P2, P3, . . . Pn per pulse are extracted in a stateshown in FIG. 4. It is judged whether or not any flat section exists inthe respective photoelectric volumetric pulse wave signals P1, P2, P3, .. . Pn.

Herein, in the process of increasing pressure in the air bag 10d at aconstant speed, in a case where the pressure in the air bag 10d is lowerthan the minimum blood pressure of a patient, the photoelectricvolumetric pulse wave signals pulsate without being influenced by thepressure of the air bag 10d (Photoelectric volumetric pulse wave signalsP1 to P6 in FIG. 4).

However, if the pressure in the air bag 10d becomes larger than theminimum blood pressure of a patient, a flat section s having no pressurefluctuation in the photoelectric volumetric pulse wave signals when theartery pressure is smaller than the pressure in the air bag 10d.Accordingly, this preferred embodiment is constructed so that aphotoelectric volumetric pulse wave signal at which a flat section soccurs for the first time is detected, and the minimum blood pressure isjudged when this photoelectric volumetric pulse wave signal P7 isdetected.

In this minimum blood pressure judgement, for example, the pressureinside the air bag 10d at the moment when the photoelectric volumetricpulse wave signal P6 immediately before the photoelectric pulse wavesignal P7 in which a flat section s occurred for the first time isextracted is made the minimum blood pressure or the mean value of thepressure inside the air bag 10d at the moment when the photoelectricpulse wave signal P7 and photoelectric volumetric pulse wave signal P6are extracted is made the minimum blood pressure.

Furthermore, in the minimum blood pressure judgement in this case, asshown in FIG. 4, if the pressure inside the air bag 10d becomes largerthan the minimum blood pressure of a patient, a high speed displacementpart K corresponding to Korotoff's sounds occurs in the photoelectricvolumetric pulse wave signals. Therefore, the photoelectric volumetricpulse wave signal in which this high speed displacement part K occurredfor the first time is detected, and it is possible to obtain the minimumblood pressure value by a method similar to the case of the flat sections.

On the other hand, in the maximum blood pressure judgement, the momentwhen the photoelectric volumetric pulse wave signal disappears is judgedas the maximum blood pressure. That is, if this pressure becomes largerthan the maximum blood pressure when increasing the pressure inside theair bag 10d at a constant speed, the moment when no photoelectricvolumetric pulse wave signal will be detected is judged as the maximumblood pressure of a patient, taking note of the artery pulsation beingsuppressed by the pressure and no displacement occurring at thephotoelectric sensor 12.

According to a cuff for a sphygmomanometer of the preferred embodiment,which is constructed as shown above, since the cuff is provided with anair bag 10d fixed at the inner circumferential side of the inside cloth10c and photoelectric sensors 12 secured inside and outside the air bag10d, the displacement quantity of a local artery wall is able to bedirectly measured by photoelectric sensors 12, and the maximum andminimum blood pressure values can be obtained on the basis of thisdisplacement quantity. Therefore, it is possible to accurately measurethe blood pressure.

Industrial Feasibility

As concretely described in the abovementioned preferred embodiment,according to a cuff for a sphygmomanometer, since it is possible todirectly measure the displacement quantity of a local artery wall byoptical range sensors and to obtain the maximum and minimum bloodpressure values on the basis of this displacement quantity, this cuff issuitable for a closed type sphygmomanometer which is able to obtain themaximum and minimum blood pressure values at a high accuracy.

What is claimed is:
 1. A cuff for a sphygmomanometer adapted forattachment to an appointed part of a patient and adapted for compressionof an artery, comprising a hard curved plate retained between an insidecloth and outside cloth sewed to each other, an engaging fastener fixedon an outer surface of said outside cloth, an air bag fixed at an innercircumferential side of said inside cloth and having an inside and anoutside, and a photoelectric sensor installed between the inside andoutside of said air bag, wherein said photoelectric sensor includes areflection plate secured at the inside part of said air bag and a lightreceiving element and a light emitting element which are provided at theoutside part of said air bag.
 2. A cuff for a sphygmomanometer as setforth in claim 1, wherein said photoelectric sensor includes a lightreceiving element and light emitting element, one of which is providedat the inside part of said air bag, and the other of which is providedat the outside part of said air bag.
 3. A cuff for a sphygmomanometer asset forth in claim 1, wherein said air bag includes a transparent bagmember and a latticed reinforcing fabric integrally incorporated in theair bag.
 4. A cuff for a sphygmomanometer adapted for attachment to anappointed part of a patient and adapted for compression of an artery,comprising a hard curved plate retained between an inside cloth andoutside cloth sewed to each other, an engaging fastener fixed on anouter surface of said outside cloth, an air bag fixed at an innercircumferential side of said inside cloth and having an inside and anoutside, and a photoelectric sensor installed between the inside andoutside of said air bagwherein said photoelectric sensor includes firstand second elements installed between the inside and the outside of saidair bag, respectively, wherein one of said elements is a light emittingelement, and the other of said elements is a reflection plate or a lightreceiving element.
 5. A cuff for a sphygmomanometer adapted forattachment to an appointed part of a patient and adapted for compressionof an artery, comprising a hard curved plate retained between an insidecloth and outside cloth sewed to each other, an engaging fastener fixedon an outer surface of said outside cloth, an air bag fixed at an innercircumferential side of said inside cloth and having an inside and anoutside, and a photoelectric sensor installed between the inside andoutside of said air bag, wherein said air bag includes a transparent bagmember and a latticed reinforcing fabric integrally incorporated in theair bag.